Method and apparatus for liquid purification

ABSTRACT

The present invention relates to a method for treating liquids, comprising the steps of irradiating a flow of air and a flow of the liquid to be treated at the same time in order to create ozone in both the air and the liquid, mixing the ozone-containing air with the liquid to be treated up-streams the liquid irradiating point, irradiating the flow of liquid containing the in-mixed ozone in order to break down the ozone in the liquid for producing free radicals.

TECHNICAL AREA

The present invention relates to a system for purifying liquid, and inparticular water, by oxidizing contaminants in the liquid.

BACKGROUND OF THE INVENTION

There is an ever increasing need for purifying liquids, and inparticular water. There are a number of applications where water needsto be purified and decontaminated, and a few of these are swimming poolsand recreational baths, green houses, animal farms, cooling towers,hospitals etc. The conventional technologies for purifying anddecontaminating water for most applications include the use of chemicalsthat are mixed with the water. Due to environmental aspects and theimpact that chemicals have on the environment, humans and animals, thereis a strive to reduce the use of chemicals.

One approach to purify/decontaminate water has been to use ozone.Several methods have been developed in several countries for purifyingwater with ozone (O₃) in drinking water installations and bathingfacilities, and also ozone dissolved in water for cleaning, disinfectionand sterilization of articles. A combination of ozone, oxygen, hydrogenperoxide and UV radiation means that the reaction proceeds much morequickly and more efficiently by virtue of the generation of more freeradicals.

The inactivation of microorganisms with the aid of ozone and radicals isconsidered as an oxidation reaction. The membrane of the micro-organismis the first to be attacked. Within the membrane/cell wall, the ozoneand the radicals destroy nuclear material inside the cell/virus/spore.The inactivation reaction in the case of most micro-organisms occurswithin minutes, depending on the ozone dose and the amount of freeradicals which are formed.

Despite its solubility in cold water, ozone is broken down (=consumed)quickly, as is the case in air, which gives a great many differentradicals and more or less stable by-products such as aldehydes, bromateand carboxylic acids. The degree of breaking down depends on the pH, thesubstance which is exposed and the temperature. Certain substances arebroken down easily by the ozone. However, the majority of substances andmolecules are oxidized more efficiently by free radicals which areformed by ozone and the media treated by ozone.

One very efficient method of using free radicals in the oxidizingprocess is disclosed in the international patent application No. WO96/20017. The method utilises UV-radiation to create ozone in air andliquid, radiates the ozone with certain wave-lengths in order to obtainfree radicals, which oxidize the contaminants in the air or liquid. Inorder to increase the production of free radicals, catalysts are used,for example titanium oxides. The applicant of the above patentapplication has obtained very good results in purifying/decontaminatingwater in cooling towers, swimming pools, green houses, to name a fewapplications. The use of the patented method has enabled a completeremoval of chemicals in those applications.

However, for certain applications, the device for purifying water orother liquids described in WO 96/20017 has capacity limitations asregards the amount to be treated per time period. Trials have been madeto reduce the flow past the UV-radiation sources, to use the device alsoduring periods when no consumption of water is taking place and to storethe purified water in intermediate tanks. This has the drawback thatadditional space has to be available in order to accommodate theintermediate tanks. For some applications this might not be feasible andfor some applications and large consumers it is not an optimal solution.There has also been a need from customers to be able to arrange thedevice so that minimal floor space is occupied.

Another application with specific problems is found in water systems inbuilding. This is in connection with legionella bacteria, a water-basedorganism which causes infection when inhaled in an aerosol form, whichis a huge problem all over the world, and is especially troublesome inhospitals, if already weak and sick people receive the bacteria via forexample showers. If the tap-water is not hot enough the bacteria maythrive and multiply uncontrolled. The main solution to this problem hasbeen to increase and to try to control the temperature of the water inorder to prevent the occurrence of legionella bacteria. Chemicals thatare able to kill these bacteria cannot usually be used for theseapplications since they may be harmful also to humans.

For certain applications, the above mentioned method has someshortcomings. If the liquid is heavily contaminated, the amount of ozonemight not be sufficient to generate the amount of radicals needed for acomplete removal of contaminants in the liquid. This may be due to thatthe radiating energy for creating ozone in the liquid either is absorbedor blocked by the contaminants or other particles/matter in the liquid.In for example treatment of salt water a lot of energy is absorbed byhalogens. Thereby not enough ozone is created and thus not enoughradicals for the purification process. There might also be the case thatthe amount of oxygen for creating ozone is insufficient.

In view of the above it would therefore be advantageous to increase theozone content in a simple and economical way using the radicals as theprimary purification oxidants. Regarding the application treating saltor brackish water it would be advantageous to use a continuous system.

There is thus a need for improvements in this technical area.

BRIEF DESCRIPTION OF THE INVENTION

The invention aims at solving the above mentioned problems with a systemaccording to the characterising part of claim 1 and 5. Preferableembodiments of the invention are covered by the dependent claims.

According to a main aspect of the invention it is characterised by amethod for treating liquids, comprising the steps of irradiating a flowof air and a flow of the liquid to be treated at the same time in orderto create ozone in both the air and the liquid, mixing theozone-containing air with the liquid to be treated up-streams the liquidirradiating point, irradiating the flow of liquid containing thein-mixed ozone in order to break down the ozone in the liquid forproducing free radicals.

According to another aspect of the invention it is characterised inexposing the fluid to at least one catalyst at the same time as theozone is broken down for increasing the amount of free radicals.

According to a further aspect of the invention, it is characterised inthat the mixing is obtained by an ejector effect into the flow ofliquid.

The advantages with the present invention are several. By irradiatingair and liquid at the same time with the same UV radiating light sourceozone is created both in the air and in the liquid, thereby avoidingseparate ozone generating sources. The ozone containing air is then fedto the flow of liquid up-streams the irradiating point, whereby amongother constituents the ozone is mixed with the liquid to be treated. Inthis way the ozone in the liquid starts to react with the contaminantsto a certain extent. The ozone-containing liquid is then irradiatedwhereby the ozone created in the liquid and the ozone mixed with theliquid is broken down to form a large amount of free radicals, whichperform the main purifying/treating action. In total larger quantitiesof ozone can be generated/contained in the liquid than if the liquid wasonly irradiated by the UV light generating means. This is especiallytrue if one compares the oxygen content between for example water andair in that air contains drastically larger quantities of oxygen thanwater. Yet the increase of ozone is performed in a simple and effectiveway without using additional ozone generating means or pre-treatmentcontainers. Because ozone is added, the previous mentioned problem withradiation energy being absorbed/blocked leading to insufficientproduction of ozone is thereby eliminated. The generating process issimultaneous in that ozone is created by the UV light generating meansin both the air surrounding the UV light generating means and in theliquid in the container at the same time as the ozone in the containeris broken down to produce radicals.

In order to further increase the amount of radicals, the treatmentpoint, for example a container where the liquid is irradiated, isarranged with catalysts capable of increasing the amount of radicals.The catalysts can consist of titanium dioxide and may be arranged on theinner surface of the container. According to one embodiment thecontainer might be manufactured from titanium, or at least lined withtitanium, which is treated in a suitable way to create titanium dioxide.A very large catalytic surface is thus created in a simple and efficientway. Furthermore, the titanium has the advantage to withstand the verycorrosive environment inside the container.

The mixing is preferably performed by using a throttle or the likedecrease of the inlet section, like for example a Venturi pipe, which iscapable of creating a negative pressure, thus creating an ejectoreffect. No special arrangements or components are thus required formixing the ozone with the liquid. The amount of the ozone to be mixedcan readily be regulated by controlling the air flow passing theUV-light generating means.

According to a further aspect of the invention it is directed to asystem for treating liquids, and in particular water, includingthrough-flowing means provided with inlets and outlets for the liquid,UV-light generating means arranged in the through-flowing means, capableof generating ozone in the through-flowing liquid and at the same timebreak down the ozone in order to produce free radicals, characterised inthat mountable and demountable connection means are arranged to theinlet and outlet of the through-flowing means.

According to yet another aspect of the invention the system ischaracterised in that it is arranged with at least two through-flowingmeans and that preferably that each through-flowing means is designed asan elongated pipe.

According to yet an aspect of the invention, the UV-light generatingmeans is arranged in one end of the elongated pipe and that ceramics isarranged on the inside of the through-flowing means at least adjacentsaid UV-generating means.

According to a preferred embodiment of the invention at least two of thesaid through flowing means are arranged in series, whereby the firstthrough-flowing means is connected to an inlet pipe for liquid to betreated and that the last through-flowing means is connected to anoutlet pipe for the treated liquid and/or are connected in parallel toan inlet pipe for liquid to be treated and an outlet pipe for thetreated liquid.

According to a further aspect of the invention the through-flowing meansis arranged adjacent a water outlet for human use like for example ashower head.

The advantages with the present invention are several. By arranging thethrough-flowing means with mountable and dismountable means it is veryeasy and convenient to vary the through-put through the system dependingon the capacity requirements. One or several through-flowing means withUV-radiating lamps can be placed after each other, ie. in series, eitherdirectly or via bends, which enables the system to be adapted to thespace available without for example taking up too much floor space. Fora substantial increase of the system one or more through-flowing meansmay be arranged in parallel with a first inlet/outlet connected to aninlet pipe and the second inlet/outlet connected to an outlet pipe.

By using the components of the system in series and/or in parallel thethrough-put may be varied almost infinitely. Several parallelarrangements of the system may be arranged in series in order to treatheavily contaminated water several times. The system is also based onstandard components and fittings and reduces the need of specialcomponents in that standard lengths of through-flowing means with lampscan be combined with standard bends and connections to the water supplythat is to be treated.

When placing a through-flowing means in connection to the outlet for ashower, one obtains the special advantage of taking care of the risk ofbeing infected with legionella bacteria. Because of the pronounced riskof legionella in large tap water systems and the difficulties ofexterminating them in such systems, the present invention removes therisk of any such bacteria leaving the water system. This is a clearadvantage over the present solutions thereby completely eliminating theproblem without any chemicals and without any risk for the users ofwater in these systems.

These and other aspects of, and advantages with, the present inventionwill become apparent from the following detailed description of theinvention and from the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

In the follow detailed description of the invention reference will bemade to the drawings, of which

FIG. 1 is a schematic side view of a first embodiment of the presentinvention,

FIG. 2 is a schematic side view of a variant of the embodiment of FIG.1,

FIG. 3 shows a central component, a through-flowing means, for treatingcontaminated liquid, comprised in a second aspect of the presentinvention,

FIG. 4 shows different components that may be included in the inventionaccording to FIG. 3,

FIG. 5 shows one example of the use of the components of FIG. 3 toobtain the present invention,

FIG. 6 shows another example of the use of the components, and

FIG. 7 shows the installation of a decontaminating unit in connectionwith a shower head.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows one embodiment of the present invention. It comprises atreatment container 10 having an inlet 12 and an outlet 14 connectableto a transport system for the liquid to be treated. Substantially thewhole inner surface is arranged with titanium, either in that thecompartment is made of titanium or that the inner surface is arrangedwith a layer of titanium, which is treated to obtain titanium dioxidefor increasing the amount of free radicals produced by the UV radiation.

The treatment to obtain titanium dioxide may for example be done byetching the titanium pipe or the layer. The titanium also has theadvantage that it is very resistant to the corrosive environment insidethe container.

A tube 16 made of quartz glass extends through the interior of thecontainer between two opposite walls 18, 20. Inside the quartz tube a UVradiating light source 21 is arranged, which extends between theopposite walls of the compartment. The light source is connected to asuitable power supply.

At one end of the quartz tube a compartment 22 is arranged, havingpassages 24 communicating with the interior of the quartz tube. Thecompartment also is provided with an air intake passage 26, whichpassage is arranged with a one-way valve 28 admitting only air onto thecompartment. Around the opposite end of the quartz tube a secondcompartment 30 is arranged. It also is arranged with passages 32communicating with the interior of the quartz tube.

A conduit 34 is connected to the second compartment. The other end ofthe conduit is connected to a section 36 of the inflow conduit 38 via aone-way valve 40, which section 36 is arranged with a narrowercross-section like a Venturi tube in order to create a ejector effectaround the connection of the conduit, as will be described below.

The device is intended to function as follows. The UV radiating lightsource is switched on, whereby it is chosen such that it emits wavelengths in the region of 180-400 nm, and in particular wavelength of183.7 nm for converting oxygen in the medium to ozone molecules (03) and254 nm for decomposing the ozone molecules, as will be described.

Air enters the quartz tube through the one-way valve in the firstcompartment and surrounds the UV generating light source. Theirradiation causes the oxygen molecules to be converted to ozone. Sincethe air flows along almost the entire length of the UV generating lightsource it is exposed to radiation for a rather long period, ascertainingthat a large quantity of ozone is created. At the same time some of theozone is broken down to free radicals by the radiation wave lengths thatdecompose the ozone to radicals.

The liquid to be treated is fed through the liquid inlet 12 and into thecontainer 10 surrounding the quartz tube 16. Because of the flow throughthe throttle section 36 of the flow conduit 38 of a Venturi-type, anegative pressure is created, whereby ozone from inside the quartz tubeis drawn into the flow of liquid via the conduit 34 and the one-wayvalve 40. The liquid that thus enters the container is mixed with ozone.

Further, the irradiation of the liquid in the container will also createozone by the UV light. Thus the liquid in the container contains bothozone that has been mixed in and ozone that has been created in thecontainer by the irradiation. In the container the liquid is irradiatedby the 254 nm wave length which causes the ozone in the liquid todecompose and hydroxyl radicals to be formed. It is a simultaneousgenerating process in that the UV light generating means generates ozonein the air and in the liquid at the same time as it generates radicalsin the liquid. The amount of radicals is further increased by thecatalytic properties of the inner wall of the container by the titaniumdioxide.

By choosing the proper flow of air through the system the amount ofozone that is mixed with the liquid at the inflow can be regulated incorrespondence with the capacity of the UV radiating light source so asto minimize the amount of residual ozone, thereby preventing that ozoneleaves the container via the outlet.

FIG. 2 shows a variant of the device of FIG. 1 intended to be used withthe modular system described in the Swedish patent application No.0202987-3, which hereby is incorporated by reference. In thisapplication one section of the device according to FIG. 2 can thenreplace two inter-connected sections according to 0202987-3. The deviceaccording to FIG. 2 can otherwise be connected in many different waysand connected with other parts, both in series and in parallel.

The invention according to the second aspect of the invention shown inFIGS. 3-7 utilises UV lamps emitting light within specific spectra. Theliquid to be treated is exposed to UV radiation with a spectraldistribution within the range of 180-400 nm. The wavelength of 183.7 nmin particular converts the oxygen in the medium to ozone molecules (O₃).The ozone molecules formed are at the same time decomposed by radiationwithin the abovementioned wavelength range, especially at a wavelengthof 254 nm. At the same time, the O₃ formed is broken down to form atomicoxygen. In order to increase the efficiency during generation of freeradicals, in particular OH⁻ radicals, oxides are added as catalysts.

The present invention utilises the principle of using free radicals forpurifying liquid, and in particular water. The system consists of atleast one substantially straight pipe, 110, FIG. 3. The pipe is made ofpreferably titanium or some other material lined with titanium on theinside. The titanium on the inside of the pipe is treated to obtain aceramic titanium oxide. The titanium oxide acts as a catalyst during theforming of free radicals, ie. the titanium oxide increases the amount offree radicals produced per time period. In one variant, a plastic pipehas been used, lined with titanium oxide. It is of course possible toutilize other highly resistant materials and to use catalysts asdescribed in WO 96/20017 but experience has shown that the use oftitanium pipes or pipes lined with titanium have provided excellentresistance against the very corrosive environment that thepurification/decontamination results in.

In the embodiment shown in FIG. 3 one end of the pipe is provided withan end wall 112. A passage 114 is arranged in the end wall and an UVradiating light source 116 is arranged in the passage with a surroundinghousing 18 extending into the passage 114, providing UV radiation withwave lengths of 185 and 254 nm. These wave lengths have excellentproperties in generating ozone in the water and then at the same timebreaking down the ozone to free radicals. The housing is preferablyprovided with light emitting wall part 120 for the convenience of theuser in displaying if the lamp is working or not. Previously a watchinghole was arranged in the pipe, which was prone to be blocked by sedimentand also to leakage. A drive unit for the UV lamps is also provided, notshown. A control unit for controlling one or several of the drive unitsis also provided, not shown. The design and function of the drive unitsand the control unit is mere routine work for the man skilled in the artand will not be described in more detail.

A first inlet/outlet 122 is arranged on the pipe wall adjacent the endwall, which inlet is arranged with suitable flanges 124 or othersuitable connection means for connection to other piping. The inside ofthe pipe is treated to obtain titanium oxide for increasing the amountof free radicals produced by the UV radiation. The treatment to obtaintitanium oxide may for example be done by etching the titanium pipe orthe layer. The end of the pipe opposite the UV lamp is arranged as thesecond inlet/outlet 126, provided with suitable flanges 128 or otherconnecting means for connection to other piping.

As shown in FIG. 4 the system comprises pipe bends 130, for example 90°or 180° but of course other angles are possible. Also these parts, eventhough not provided with any UV-radiation means, are preferably made oftitanium or lined with titanium. FIG. 4 also shows a few connectionalternatives for combining the components of the system, like connectingtwo straight pipes by inter-connecting their second inlets/outletseither directly like in 132, via a 90° bend like in 134 or via a 180°bend like in 136.

FIGS. 5 and 6 show a “parallel-connected” system where two straight pipesections 132, 134, 136 provided with UV lamps are inter-connected withtheir second inlets/outlets to each other, so in fact there is a“back-flow” in one of the pipes. Several of these inter-connected pipesare placed in parallel where the first inlets/outlets 122 of one of theinter-connected pipes are connected to a common inlet pipe 140 and wherethe first inlets/outlets of the other inter-connected pipes areconnected to a common outlet pipe 142. In this case the water to betreated is fed via the inlet pipe 140, where the opposite end of theinlet pipe is closed by a wall 144, and in parallel through theinter-connected pipes 132 where the water is irradiated by the UV-lampsof both pipes. The water is then fed through the water outlet pipe 142.In the same manner the end of the outlet is closed by a wall 144.

The configuration enables both an increased capacity in that a largenumber of pipes including UV-radiating means can be connected dependingon application and capacity requirements and also that walls andceilings may be taken into use for setting up the system. In otherwords, very little floor space has to be utilized, which may be ofimportance for applications where space is limited. With the componentsit is further easy to adapt the system to existing layout of the spaceto be used, rather than to rebuild the space in order to fit thepurifying system.

FIG. 6 shows another example where three parallel-connected units havebeen connected to main inlet and outlet pipes, where the units have beenplaced on the walls and ceilings and also around corners. The system isthus very versatile. It is to be understood that other designs of thecomponents of the pipe system may be used without departing from thescope of the invention.

In this context it is also to be understood that lamps with differentpower may be used and that additional oxygen may be added by appropriatemeans in order to increase the amount of ozone and thus of freeradicals. When the water is heavily contaminated, or when large amountsof free radicals in the water is needed, it is also conceivable toinclude an ultrasonic device placed in the vicinity of the UV-lamps.High amplitude ultrasonic waves generate free radicals and breakcontaminants.

One specific application where the system of the present invention maybe utilized is for preventing legionella bacteria in connection withshowers, which is a potential infection point because the bacteria maycause infection when inhaled in an aerosol form. In the embodiment shownin FIG. 7 a pipe 170 including an UV-amp as described above is connectedto the outlet of a water faucet 172 in a shower or similar water outlet.The water from the faucet is led through the pipe where it is irradiatedby the UV-lamp whereby ozone is created, and whereby at the same timethe ozone is broken down into free radicals, which react with anddestroys the legionella bacteria. The number of free radicals isincreased by the titanium oxide on the inside of the pipe. In thiscontext it is to be pointed out that the life span of the free radicalsis extremely short and there is thus no risk whatsoever that freeradicals can exit through the shower head 174. The inclusion of adisinfecting system according to the invention completely removes therisk of legionella bacteria to be spread to humans. It is also to benoted that in contrast to most devices using UV-light sources, where thelight is switched off during non-use due to eg. energy consumption, thepresent device is switched on all the time in order to ensure that nolegionella bacteria can pass the device and settle beyond the it. Thisis feasible due to the very low energy consumption needed for thisparticular application.

As an alternative, the pipe 176 may of course be connected to the inletof the warm water 178 to the faucet 170, ie. before but in connectionwith, the faucet.

It is to be understood that the embodiments described above and shown inthe drawings are to be regarded as non-limiting examples of theinvention and that the scope of protection of the invention is definedby the patent claims.

1. Method for treating liquids, comprising the steps of irradiating aflow of air and a flow of the liquid to be treated at the same time inorder to create ozone in both the air and the liquid, mixing theozone-containing air with the liquid to be treated up-streams the liquidirradiating point, irradiating the flow of liquid containing thein-mixed ozone in order to break down the ozone in the liquid forproducing free radicals.
 2. Method according to claim 1, comprising thefurther step of exposing the fluid to at least one catalyst at the sametime as the ozone is broken down for increasing the amount of freeradicals.
 3. Method according to claim 1, wherein the UV radiation whichis emitted for breaking down the ozone and contaminants has a wavelengthof 245 nm-400 nm.
 4. Method according to claim 3, wherein the UVradiation which is emitted for breaking down the ozone has a wavelengthof 254 nm.
 5. Method according to, wherein the mixing is obtained by anejector effect into the flow of liquid.
 6. Apparatus for treatment ofliquid according to claim 1, comprising a container having an inlet andan outlet for the liquid to be treated, UV generating light sourcecapable of irradiating the inside of the container, air guidance meansarranged inside the container, connected to an air source and an inletconduit for the liquid to be treated via a mixing means.
 7. Apparatusaccording to claim 6, wherein said air guidance means comprises acompartment divided from the inside of the container by a quartz glassand that said UV light radiating means is arranged in or adjacent saidcompartment.
 8. Apparatus according to claim 6, wherein substantiallythe whole of the inner surface is arranged with a catalyst.
 9. Apparatusaccording to claim 8, wherein the catalyst comprises titanium dioxide.10. Apparatus according to claim 6, wherein the mixing means comprises athrottle on the inlet, which throttle is capable of creating an ejectoreffect of the air/ozone into the flow of liquid.
 11. Apparatus fortreating liquids, and in particular water, according to claim 6, furtherincluding through-flowing means provided with inlets and outlets for theliquid, UV-light generating means arranged in the through-flowing means,capable of generating ozone in the through-flowing liquid and at thesame time break down the ozone in order to produce free radicals,characterised in that mountable and demountable connection means arearranged to the inlet and outlet of the through-flowing means. 12.System according to claim 11, characterised in that it is arranged withat least two through-flowing means.
 13. System according to claim 12,characterised in that said through-flowing means are arranged in series,whereby the first through-flowing means is connected to an inlet pipefor liquid to be treated and that the last through-flowing means isconnected to an outlet pipe for the treated liquid.
 14. System accordingto claim 12, characterised in that at least two of the said throughflowing means are connected in parallel to an inlet pipe for liquid tobe treated and an outlet pipe for the treated liquid.
 15. Systemaccording to claim 11, characterised in that the through-flowing meansis designed as an elongated pipe.
 16. System according to claim 15,characterised in that the UV-light generating means is arranged in oneend of the elongated pipe.
 17. System according to claim 11,characterised in that ceramics is arranged on the inside of thethrough-flowing means at least adjacent said UV-generating means. 18.System according to claim 17, characterised that the ceramics istitanium oxides.
 19. System according to claim 11, characterised in thatthe through-flowing means is arranged adjacent a water outlet for humanuse, like a shower head.
 20. System according to claim 19, characterisedin that the through-flowing means is arranged between a water faucet andthe water outlet.
 21. System according to claim 19, characterised inthat the through-flowing means is arranged between a warm water pipe anda faucet connected to the water outlet.